It is proposed to study the immunochemistry and pathogenic role of gonococcal pili. This is a continuation and extension of previous research by Dr. Buchanan at the Rockefeller University during 1971-1975, under support of grant AI 10615-04. Immunologic studies will focus on comparison of the antigen(s) of purified pili from different strains of gonococci, meningococci and other Neisseria. The principal method used will be competitive inhibition of an immunoassay for pili using known weights of purified pili from the same and different strains of Neisseria. Chemical studies will include completion of analysis of the size, charge, density and chemical characteristics of purified gonococcal pili, characterization of purified pili from different gonococcal strains and meningococci, and studies of the pilar attachment moiety and the tissue receptor site for gonococcal pili. Methods will include sodium dodecyl sulfate slab polyacrylamide gel electrophoresis, peptide mapping, amino acid composition, and sequence determinations on important peptides of gonococcal pili. Studies of the pathogenic role of pili will focus on the attachment of gonococcal pili to mammalian cells. The conditions and kinetics of this attachment will be examined and the effects of antibody to pili or cell receptor sites will be studied. Purified pili will be used and followed by radiolabelling, immunoassay, and direct electron microscopic observation. BIBLIOGRAPHIC REFERENCES: Buchanan TM: Attachment of purified gonococcal pili to latex spheres. In Microbiology, 1976. Schlessinger D (ed). Amer Soc Micro, Wash., D.C. pp 491-493, 1976. DiGiacomo RF, Gale JL, Homes KK, Buchanan TM: Urethral inoculation of male baboons with Neisseria gonorrhoeae. Infect and Immun, 15:670-671, 1977.